Measurement of lipid composition in human skeletal muscle and adipose tissue with ¹ H-MRS homonuclear spectral editing

Purpose: Accumulation of triglycerides in nonadipose tissue (e.g. ectopic lipids) is characteristic of metabolic derangements and is linked to insulin resistance and cardiovascular disease. Although the detrimental effects of the total amount of ectopic fat has been established, the role of composition of the ectopic lipid stores is unknown. In this study we used proton magnetic resonance spectroscopy (¹ H-MRS) homonuclear spectral editing to characterize lipid stores in adipose tissue and skeletal muscle at 4 T.

Methods: A MEGA-sLASER sequence was used to selectively detect lipid resonances that are scalar coupled to the methine resonance at 5.31 ppm and that can be used to estimate saturated fatty acid and mono- and polyunsaturated fatty acids. Phantom experiments were performed to empirically determine correction factors for editing efficiency of the different lipid groups.

Results: The spectral editing approach enabled the estimation of saturated, mono-unsaturated, and polyunsaturated fatty acid contributions in phantoms and in vivo. These estimations are in the same order as reported in studies using invasive biopsies.

Conclusions: In this study, we have shown the feasibility of spectral editing techniques for ectopic lipid store characterization with ¹ H-MRS, regardless of spectral resolution (e.g., B_0- field strength). This new approach offers the opportunity to study ectopic lipid composition in relation to metabolic diseases. Magn Reson Med 79:619-627, 2018. © 2017 International Society for Magnetic Resonance in Medicine.